Plan 9 /sys/man/1/prof

NAME

prof, tprof, kprof – display profiling data

SYNOPSIS

prof [ –dr ] [ program ] [ profile ]
tprof pid
kprof kernel kpdata

DESCRIPTION

Prof interprets files produced automatically by programs loaded using the –p option of 8l(1) or other loader. The symbol table in the named program file (2.out etc., according to $objtype, by default) is read and correlated with the profile file (prof.out by default). For each symbol, the percentage of time (in seconds) spent executing between that symbol and the next is printed (in decreasing order), together with the time spent there and the number of times that routine was called.
Under option –d, prof prints the dynamic call graph of the target program, annotating the calls with the time spent in each routine and those it calls, recursively. The output is indented two spaces for each call, and is formatted as

symbol:time/ncall

where symbol is the entry point of the call, time is in milliseconds, and ncall is the number of times that entry point was called at that point in the call graph. If ncall is one, the /ncall is elided. Normally recursive calls are compressed to keep the output brief; option –r prints the full call graph.
The size of the buffer in program used to hold the profiling data, by default 2000 entries, may be controlled by setting the environment variable profsize before running program. If the buffer fills, subsequent function calls may not be recorded.
The profiling code provided by the linker initializes itself to profile the current pid, producing a file called prof.pid. If a process forks, only the parent will continue to be profiled. Forked children can cause themselves to be profile by calling

prof(fn, arg, entries, what)

which causes the function fn(arg) to be profiled. When fn returns prof.pid is produced for the current process pid.
The environment variable proftype can be set to one of user, kernel, elapsed, or sample, to profile time measured spent in user mode, time spent in user+kernel mode, or elapsed time, using the cycle counter, or the time in user mode using the kernel's HZ clock. The cycle counter is currently only available on modern PCs and on the PowerPC. Default profiling measures user time, using the cycle counter if it is available.
Tprof is similar to prof, but is intended for profiling multiprocess programs. It uses the /proc/pid/profile file to collect instruction frequency counts for the text image associated with the process, for all processes that share that text. It must be run while the program is still active, since the data is stored with the running program. To enable tprof profiling for a given process,

echo profile > /proc/pid/ctl

and then, after the program has run for a while, execute

tprof pid

Since the data collected for tprof is based on interrupt–time sampling of the program counter, tprof has no –d or –r options.
Kprof is similar to prof, but presents the data accumulated by the kernel profiling device, kprof(3). The symbol table file, that of the operating system kernel, and the data file, typically /dev/kpdata, must be provided. Kprof has no options and cannot present dynamic data.

SOURCE

/sys/src/cmd/prof.c /sys/src/cmd/kprof.c